Local seal for encapsulation of electro-optical element on a flexible substrate

ABSTRACT

An electroluminescent display or lighting product incorporates a panel including a collection of distinct light-emitting elements formed on a substrate. A plurality of distinct local seals are formed below respective individual light-emitting elements or groups of light-emitting elements. Some embodiments combine a metal foil substrate and glass local seals in a flexible bottom-emitting product. The local seal may be used in conjunction with a continuous thin film encapsulation structure. Optical functions can be provided by each local seal, including refraction, filtering, color shifting, and scattering. Each local seal is formed by depositing a low melting temperature glass powder suspension or paste using inkjet technology, and fusing the glass powder using a scanning laser beam having a tailored beam profile. In other embodiments, a lower encapsulation substrate incorporating local window seals is wholly or partially pre-formed.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent is a continuation-in-part of commonly assigned, co-pendingU.S. patent application Ser. No. 14/446,470, filed Jul. 30, 2014, titled“Local Seal For Encapsulation Of Electro-Optical Element On A FlexibleSubstrate” by Rohatgi, since published as U.S. 2015/0034934 A1, whichclaims the benefit of U.S. Provisional Application 61/859,989, filedJul. 30, 2013.

FEDERALLY SPONSORED RESEARCH

Not applicable.

FIELD OF THE INVENTION

The present invention relates to encapsulation of a flexibleelectroluminescent device or similar electro-optical panel.

BACKGROUND

Electro-optical arrays are widely used in commercial products. Examplesof such products include a phone, a monitor, a television set, and awristwatch, all of which have pixel arrays used for information display.Further examples include an OLED lighting panel and an OLED luminaire,which have arrays of OLED elements used for illumination.

Display Products

In recent years, there has been a blurring of lines between some of theabovementioned product categories. For example, modern smartphonesroutinely include cameras and allow viewing of video and televisionreceived over wireless networks and the Internet. Additionally,smartphones offer access to many of the same classes of applications(or, “apps” for short) that consumers previously accessed usingcomputers with monitors. These application classes include news, email,instant messaging, games, and office productivity tools. Therefore,within this disclosure, we mean “phone” as commonly understood atpresent: a relatively small devices with display less than or equal to30 cm in extent, preferably less than or equal to 20 cm in extent, morepreferably less than or equal to 15 cm in extent, and commonly less thanor equal to 10.2 cm in extent. The term “extent” means the largesttransverse dimension of an active region along a surface of a display,lighting device, or other electro-optical array. For rectangulardisplays as are found in common phones and televisions, the extent isthe same as the diagonal measure commonly cited as the size of thedisplay. For curved products, “extent” is measured as if the product waslaid out flat.

The term “array”, as applied to electro-optical or electroluminescentelements, is understood to refer to a two-dimensional array of suchelements formed over a single substrate. A two-dimensional layout ofOLED panels, each having a single electroluminescent element would notbe considered an array of electroluminescent elements, since each OLEDpanel has a different substrate from the other OLED panels. The array isconsidered to be two-dimensional regardless of whether the surface isflat or curved. The surface on the substrate over which such an array isformed is nominally considered to be the top surface of the substrate,regardless of the orientation or curvature of the substrate within aparticular product.

It is also useful to define the concept of neighboring elements in suchan array. Consider first and second elements of such an array, whichhave respective first and second centroids. The first and secondelements are neighbors if the number of distinct points on the topsurface of the substrate that are (a) equidistant from first and secondcentroid, and (b) farther from the centroids of all other elements ofthe array, is greater than or equal to two. According to this definitionof “neighbor” two adjacent squares on a chessboard are neighbors (allexcept corner points along their common boundary satisfy both conditions(a) and (b)), two diagonally touching squares on the chessboard are notneighbors (the corner where the squares touch is equidistant from foursquares of the chessboard, hence this point does not satisfy condition(b), and no other point meets both conditions (a) and (b) either), andtwo squares remote from each other on the chessboard are not neighbors(all points satisfying condition (a) are closer to the centroid of somethird square than to the first and second centroids).

We use “television” as commonly understood in the art: a relativelylarge device for playing video-plus-audio programming received fromover-the-air broadcast, cable TV, the Internet, wireless network, or bywired transmission from separate nearby equipment such as an opticaldisk player, a digital video recorder, a computer, or a camera. Thedisplay of a television may range from 2 cm to 305 cm in extent,preferably 20 cm to 255 cm, commonly 30 cm to 155 cm, and often 80 cm to140 cm in extent.

We use “monitor” to mean a display capable of showing changinginformation over time. Monitors include those found in airportterminals, lobbies of commercial buildings, and kiosks, as well as thoseassociated with a specific computing device such as a tablet, a laptop,or a desktop computer, or otherwise known in the art. “Monitor” may alsorefers to an information display found in or on a host of embeddedsystems, ranging from thermostats, refrigerators, automobiles, GPSnavigation devices, alarm systems, and many more. Small informationdisplay monitors may have an extent from 0.1 cm to 75 cm, preferablygreater than equal to 2 cm, commonly greater than or equal to 20 cm, andoften greater than or equal to 50 cm. Large information display monitorsoften have an extent from 75 cm to 200 cm, preferably less than or equalto 155 cm. Ultra-large information displays are also known. For example,sports stadiums commonly have displays exceeding 100 m² in area; thestadium exterior display built for the Kazan Universiade measures anastonishing 3700 m². Of course, these ultra-large displays oftencomprise a modular array of smaller information display monitors. Insuch a case, the term “monitor” includes within its scope both theentire stadium display, as well as a single module. In other cases,large information displays are comprised of discrete lamps. A lamp isunderstood herein to mean a single light-emitting element that cannot bespatially resolved as smaller elements. A lamp is not a monitor, asunderstood herein. A monitor may be a commercial product by itself, suchas a stand-alone monitor for a desktop computer, or it may be part of anintegrated system, such as the information display of a tablet computer.

There is a burgeoning class of commercial products known as wearableelectronics, many of which incorporate a display. Wristwatches have beencommon for over one hundred years, and electronic wristwatches have beenknown for over forty years. Recently, watches with full-color displayshave emerged in the marketplace. Other wearable electronic devices withdisplays include personal music players (such as the Apple iPod™), andhead-mounted optical displays (such as the Google Glass™). There havebeen proposals to incorporate wearable electronics into clothing, shoes,jewelry, and other articles of apparel.

All of these commercial products may have displays that are full-coloror monochromatic; black and white displays being a special case ofmonochromatic displays. Displays commonly incorporate individualelements, known as pixels, on a common substrate. Typically, pixels areelectrically controlled and are individually controlled, however pixelsmay be commonly controlled in groups. In an electroluminescent display,such as an OLED display, pixels are individually light-emitting. Otherdisplays have a common light source for multiple pixels, which could bea backlight or edge lighting or ambient light. One common light sourcemay illuminate all the pixels of the display, or merely a group ofpixels in a region of the display. In displays with one or more commonlight source, the individual pixels incorporate electro-optical elementsthat control the transmission or reflection of light from the one ormore common light source. Displays of this type include liquid crystaldisplays, electrochromic displays, ferro liquid displays,electrophoretic displays, and electrowetting displays. The term“electro-optical element” includes electroluminescent elements such asLED and OLED. Many of these electro-optical elements contain organicmaterials and have limited tolerance for heat. Many of theseelectro-optical elements are sensitive to moisture and oxygen. OLEDelements are particularly sensitive to moisture, are sensitive tooxygen, and have limited tolerance for heat. While heat tolerance of anOLED varies according to the device architecture and the particularcompounds used, 300° C. has been cited as a maximum substratetemperature during an encapsulation process, by Federovskaya in U.S.Patent Application Publication 2009/0081356 A1.

Lighting Products

Electro-optical arrays, in particular electroluminescent arrays, alsofind use in lighting products. The term “lighting product” refers to anyproduct whose function is to provide illumination of space or objectsexternal to the product. Illumination may be in the visible spectrum orin other portions of the electromagnetic spectrum. OLED panels may belighting products; OLED lighting panels are commonly organized as anarray of commonly controlled but separate light emitting elements on asingle substrate. At present, the extent of the array of light emittingelements in an OLED panel may lie within the range from 2 cm to 30 cm,commonly 5 cm to 21 cm, and often 10 cm to 16 cm. In future, asmanufacturing technology improves, this array extent may increase to 50cm, 100 cm, or even larger. In some instances, OLED panels may havelight-emitting elements having a plurality of differently coloredemissions. For example, ⅓ of the elements may be red, ⅓ green, and ⅓blue. By varying the relative excitation of red, blue, and greenelements, the color and the color temperature of the light may becontrolled. Light emitting elements in an OLED panel are commonlyorganized in rectangular or hexagonal layouts. Although many or all ofthe light emitting elements in an electroluminescent array of a lightingproduct are commonly controlled, from the point of view of structure andorganizational layout, these light emitting elements are substantiallysimilar to the pixels of a display product. Furthermore, for any givenelectroluminescent technology, the encapsulation requirements of lightemitting elements in display and lighting products are substantiallysimilar. Since encapsulation is of particular interest in thisdisclosure, it is understood that discussions using the term “pixel” aregenerally applicable to lighting elements of a lighting product as well,except in those cases where it is clear from the context that thediscussion is specific to display products only.

Because OLED panels are at present relatively small, and becausedesigners have exercised their imagination to create complex andartistic structures, many lighting fixtures and luminaires have beenconceived as each comprising multiple OLED panels. Such a lightingfixture or luminaire would be a commercial product incorporating aplurality of electro-optical arrays, since each OLED panel itselfincorporates an electroluminescent array. A lighting fixture orluminaire is understood to mean a single detachable assembly directlymounted onto a wall, ceiling, floor, furniture, building, frame, pole,tower, truss, or other civil structure, for the purpose of providingillumination. A lighting panel is understood to mean the smallestremovable unit from a lighting fixture or luminaire that can be removedand replaced as an integral unit without impairing the capacity of thisunit to generate light, in other words, without breaking anything.Although lighting panels and lighting fixtures are often distinct, theycan also be the same, for example the common inexpensive plug-inelectroluminescent night lights available today. Of course, depending onthe electroluminescent technology in use, not all electroluminescentpanels will incorporate a two-dimensional array of separate lightemitting elements; some technologies may readily allow a panel to bebuilt as a single light-emitting element, or alternatively as aone-dimensional array of light-emitting elements.

Flexible Products

Another current trend is toward flexible products. From a manufacturer'sstandpoint, flexible products are desirable because they can bemanufactured at large scale and high volume using a relativelyinexpensive roll to roll process, as against the more common discretemanufacturing used today for both display and lighting products. From adesigner's standpoint, flexible products are desirable because they canbe configured into curved devices, some of which will be rigid curveddevices, such as a curved television, while others will be flexible,such as could be integrated into clothing. From a consumer's standpoint,flexible products are desirable because they offer the prospect oflightweight, compact, foldable, and even unbreakable devices.

However, as discussed below, encapsulation suitable for flexibleproducts has not been satisfactorily addressed to date, especially forthe stringent encapsulation requirements of OLED elements.

Encapsulation Technology

Materials used in organic light emitting diodes (OLEDs) are well knownto be sensitive to oxygen and moisture. Degradation mechanisms aredescribed, for example, by So et al., Advanced Materials, vol. 223, pp.3762-3777, 2010. As a result, encapsulation is an important part of OLEDdesign. Two main classes of encapsulation are known: (1) use of anencapsulation substrate, i.e. a preformed sheet, and (2) thin filmencapsulation.

Encapsulation substrates may commonly be glass or metal, and arecommonly spaced from underlying electroluminescent elements with e.g.nitrogen gas fill in between. For example, U.S. Pat. No. 6,111,357 to P.Fleming describes an encapsulation substrate in the form of a glass,metal, or ceramic cover that is attached to an underlying displaysubstrate by a perimeter seal located outside the active area of thedisplay. A metal substrate is opaque and is only suitable for abottom-emitting display, while a glass substrate is relatively thick andrigid, and not well-suited for roll-to-roll manufacture or flexibledisplays.

A wide variety of glass-to-metal seals are known. Some metals (forexample, platinum, nickel, zirconium, and indium) can be adhered toglass directly. Many metals (for example copper, silver, nickel, andmolybdenum) form strong joints with glass via an intermediate layer ofmetal oxide. Many alloys (including stainless steel) can be bonded toglass via an intermediate oxide layer of one or more of the metalconstituents of the alloy. Strong bonds can also be formed with othercompounds joining the metal to the glass, such as chromium silicide.Other metals (for example, aluminum) are difficult to bond to commonsilica-based glasses, but can be bonded to special glass formulations(for example, phosphate glasses).

Thin film encapsulation offers manufacturing benefits, but suffers fromthe relatively high permeability of polymer materials, and thedifficulty of depositing or forming thin film layers that are free ofpinholes. The permeability requirements for OLED are stringent and limitthe choice of suitable materials. One approach to overcoming theseproblems has been preparation of laminated layers. See, for example,U.S. Pat. No. 4,104,555 to G. Fleming, U.S. Pat. No. 5,811,177 to Shi,and Lewis et al., IEEE Journal of Selected Topics in QuantumElectronics, vol. 10, no. 1, pp. 45-57, 2004. But, the use of laminatedlayers requires additional process steps, with attendant costs.

Additionally, many variants are known. In U.S. Patent ApplicationPublication 2012/0319141, Kim discloses a combination of a multi-layerthin film seal with a cover attached by a perimeter seal. U.S. Pat. No.7,368,307 to Cok discloses a flexible substrate attached to a rigidcurved encapsulating cover. Neither of these solve the abovementionedproblems with encapsulation substrates on one hand, or thin film sealson the other.

It is also known to combine the encapsulant function with otherfunctions. In U.S. Patent Application Publication 2011/0241051, Carterdiscloses a structured film encapsulant with an integrated microlensarray and diffraction grating. This encapsulant is pre-formed, whichentails additional manufacturing equipment and cost, and also requirescareful alignment between the pre-formed optical structures on theencapsulant and a pixel pattern on an underlying display substrate.Further, Carter's encapsulant is described as comprising an elastomericpolymer (such as polydimethylsiloxane (PDMS)) with one or two coatinglayers (such as silicon nitride (SiN)). This multi-layer structureinvolves additional process steps and costs as described above.

A number of authors have been concerned with the separate encapsulationof distinct devices on a mother glass, prior to singulation. U.S. Pat.Nos. 7,091,605, and 7,329,560 both require a perimeter seal around eachdistinct device, which requires too much space to be workable betweenneighboring electro-optical elements in a two-dimensional array ofelements of a single device. U.S. Pat. No. 6,949,382 to Pichler requireshardening of a planarization layer that substantially covers an entiredevice, and is fundamentally at odds with encapsulating a flexibledevice.

Thus, there remains a need for an encapsulation technology that iscompatible with roll-to-roll manufacturing, and flexible, unbreakable,or deformable products that incorporate a two-dimensional array ofelectro-optical elements.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods forencapsulation of an electroluminescent product comprising a collectionof distinct light-emitting elements such as pixels.

In a first aspect, local encapsulation seals are provided underrespective individual light-emitting elements. In accordance withpreferred embodiments of the present invention, the local encapsulationseals are formed of a glass material. The advantages of glass includelow permeation rates for both moisture and oxygen, as well as opticalclarity. See, for example, U.S. Pat. No. 7,026,758 to Guenther. Theseadvantages can be retained by forming a local glass seal below eachlight-emitting element. Because the glass need not be a continuoussheet, flexibility of a finished light-emitting product is notcompromised.

In a second aspect, local encapsulation seals are provided underrespective groups of light-emitting elements. In a third aspect of thepresent invention, the size of each local glass seal is compatible withthe flexibility requirement of the application.

In a fourth aspect of the present invention, local glass seals areformed as windows in a matrix. In this disclosure, the term “matrix” isused in its sense of “a surrounding medium or structure”, that is amatrix may be in sheet form having openings in which local seals may beprovided. In preferred embodiments, the matrix comprises metal. In someembodiments, the metal is in the form of a flexible foil. In otherembodiments, the metal matrix is rigid. The matrix may be a singlehomogeneous layer, a laminate, or a composite structure. The matrixopenings may be formed before, after, or independently of formation ofelectro-optical elements.

In a fifth aspect, each individual light-emitting element is a pixel(sometimes called a subpixel) of a display product. In a sixth aspect,each individual light-emitting element is a distinct element of acollection of such elements forming a lighting product.

Henceforth in this document, the term pixel will be used to denote adistinct light-emitting element in any of a display product or alighting product. In preferred embodiments, a distinct light-emittingelement is an organic light-emitting diode, or OLED, however theinvention is not limited to OLED products. The term distinct is used toindicate that a light-emitting element is physically separated fromother light-emitting elements. For both display and lighting products,the product may have many such distinct light-emitting elements formedtogether integrally as a two-dimensional array of elements on a singlesubstrate. Two distinct light-emitting elements in a product may becontrolled by same or different circuitry, and may or may not beoperable independently of one another.

In a seventh aspect of the present invention, local encapsulation sealsare formed both above and below a two-dimensional array ofelectro-optical elements in a panel. In some embodiments, theelectro-optical elements are emissive, and the panel emits light fromboth top and bottom. In other embodiments, the electro-optical elementscontrol light transmission, and the panel receives incident lightthrough at least one of its top and bottom surfaces, and lightcontrolled by the array of electro-optical elements is emergent from anopposite surface.

In an eighth aspect of the present invention, the local seals may becombined with a thin film encapsulation structure. In some embodiments,the thin film encapsulation structure is formed before formation oflocal seals, while in others the thin film encapsulation structure isformed after local seals. In some embodiments, the thin filmencapsulation structure comprises a single layer, while in otherembodiments, the thin film encapsulation structure comprises multiplelayers. In some embodiments, the thin film encapsulation structure alsoserves as a planarization layer.

The combination of a thin film encapsulation structure with local sealsis mutually beneficial. The local seals provide protection against pixeldamage due to pinhole defects in the thin film encapsulation structure,particularly since pixels are most sensitive to pinhole defects directlybelow or above the pixel. Conversely, the thin film encapsulationstructure reduces uptake of moisture or oxygen by areas of internallayers between the pixels. While such uptake of moisture or oxygen maynot directly impact performance of a display or lighting product, themoisture or oxygen so absorbed can migrate laterally into the activearea of a light-emitting element, where the moisture or oxygen willlikely impact product performance. Thus, the thin film encapsulationstructure can greatly improve protection of a light-emitting elementagainst secondary paths of moisture or oxygen ingress.

In a ninth aspect of the present invention, local glass seals are formedusing a suspension or paste of glass powder. In a tenth aspect, theglass powder used has a low fusing temperature, which may be less thanor equal to 300° C. Glass powders with low fusing temperatures in therange 220-300° C. have recently become available. These meltingtemperatures are compatible with many OLED materials. An example of sucha powder with melting temperature in the range 220-300° C. has beenadded to Hitachi Chemical's Vaneetect product line. See, for example,Hitachi News Release, “220-300° C. low-melting glass for hermeticsealing”, Nov. 26, 2012, http://www.hitachi.com/New/cnews/121126a.pdf.

In an eleventh aspect of the present invention, the local seals mayadditionally perform a lens function. In some embodiments, a local sealhas substantially planar top and bottom surfaces, and performs no lensfunction. In other embodiments, a local seal has a curved top or bottomsurface and acts as a converging lens. A converging lens function isdesirable, for example, in a battery-powered personal device, wherelight emitted in directions away from a user represents wasted energyand reduced battery life. In still other embodiments, a local seal has acurved top or bottom surface and acts as a diverging lens. A diverginglens function is advantageous, for example, in television products,digital signage, and some lighting products, where wide field of view isdesirable.

In a twelfth aspect of the present invention, the local seals mayadditionally perform a different optical function, such as a filter, acolor converter, and/or a scatterer. In some embodiments, the local sealis formed of a glass powder suspension doped with one or more pigments,so as to tailor the emission profile with respect to the naturalemission profile of the underlying electroluminescent element. Thisaspect of the invention is advantageous for display products having acommon emissive layer for different color pixels. This aspect of theinvention is also advantageous for lighting products to tailor the colortemperature of the emitted light. In some embodiments, the glass powdersuspension is doped with a fluorescent or other color shifting material.This aspect of the invention is advantageous, for example, in a lightingproduct, to convert cold bluish light to a warmer color. In someembodiments, the glass powder suspension may be mixed with a powder of arefractory material. When the glass is fused during manufacture of thelocal seals, the refractory materials remain intact. Thereby the localseals lose some of their optical clarity and take on a scatteringfunction.

In a thirteenth aspect of the present invention, the glass powdersuspension or paste is deposited using inkjet technology. Glass powdersare widely used in industry, and are commonly applied in the form of asuspension or a paste. Inkjet technologies have already been proposedfor deposition of electroluminescent materials in a light-emittingpixel, for example by Duineveld in U.S. Pat. No. 7,011,561. The sametechnology can be applied for deposition of a glass powder suspension orpaste above or below a pixel or other small light-emitting element. InU.S. Pat. No. 6,855,367, Nakao describes a glass powder jet ink.

In a fourteenth aspect of the present invention, the deposited glasspowder is fused without damaging any overlaid TFT or electroluminescentlayers. In some embodiments, fusing of the glass powder can be achievedby bulk heating of the entire product. In other embodiments, fusing ofthe glass powder can be achieved by uniformly heating a surface of theproduct on which local seals are being formed. In yet other embodiments,heat is deposited locally so that the areas to be sealed absorb moreenergy per unit area than areas between seals.

In a fifteenth aspect, a laser source producing a tailored beam profileis used to provide non-uniform irradiation of the product surface onwhich local seals are being formed. In a range of embodiments, thetailored beam profile may be a spot, a group of distinct spots, or aline.

In a sixteenth aspect, local glass seals are formed prior to formationof electro-optical elements. In some embodiments, local glass seals maybe formed prior to formation of any TFTs.

Additionally, embodiments of the present invention are known with localglass seals, that do not depend on in situ seal formation from a glasspowder.

In a seventeenth aspect, part or whole of an encapsulation substrate ispre-formed. In some embodiments, local glass sealing windows are formedof pre-formed glass, which are attached to respective openings in amatrix. In some embodiments, glass-in-metal window elements arepre-formed, and joined together by welding or soldering to produce theencapsulation substrate. In some embodiments in which the entireencapsulation substrate is pre-formed, active elements (including TFTsand electroluminescent elements) may be formed subsequently over theencapsulation substrate, while in other embodiments, an array of activeelectro-optical elements is formed separately from the encapsulationsubstrate, which are then attached. In some embodiments in whichportions of the encapsulation substrate are pre-formed, these portionscan be assembled onto the array of active electro-optical elements tobuild up the complete encapsulation substrate. In other embodiments,pre-formed portions of the encapsulation substrate can be combined toform a complete encapsulation substrate prior to attachment or formationof active electro-optical elements.

The skilled practitioner will recognize that above-mentioned aspects ofthe present invention can be variously combined to suit a particularapplication or manufacturing process. Furthermore, these aspects canalso be combined with yet other features not enumerated herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description will be better understood when readin conjunction with the appended drawings, in which are shown some ofthe multiple embodiments of the present invention. It should beunderstood that the various embodiments of the present invention are notlimited to the precise arrangements and instrumentalities shown in thedrawings. Further, dimensions of the features shown are often widelydisparate; the drawings are not to scale.

FIG. 1 is a diagram of a prior art device encapsulated using anencapsulation substrate.

FIG. 2 is a diagram of a prior art device encapsulated using a thin filmencapsulation.

FIG. 3 is a diagram of a first embodiment of the present inventionhaving local glass seals below electro-optical elements of a panel suchas a display panel.

FIG. 4A is a diagram of a second embodiment of the present inventionhaving local glass seals below light emitting elements of a lightingpanel.

FIG. 4B is a diagram showing a cross-sectional view of the embodiment ofFIG. 4A.

FIG. 5 is a diagram of a third embodiment of the present inventionhaving local glass seals below groups of light emitting elements.

FIGS. 6A-6F are diagrams of an electroluminescent panel at differentstages of formation of local glass seals.

FIGS. 7A-7C are diagrams showing different forms of heating that may beused to fuse local glass seals.

FIGS. 8A-8C are diagrams of different laser beam profiles that may beused for selective heating of glass seals.

FIG. 9 is a diagram of a fourth embodiment of the present inventionhaving thin film encapsulation below local glass seals.

FIG. 10 is a flow chart showing process steps for manufacture of thefourth embodiment.

FIG. 11 is a diagram of a fifth embodiment of the present inventionhaving local glass seals below a thin film encapsulation layer.

FIG. 12 is a flow chart showing process steps for manufacture of thefifth embodiment.

FIGS. 13A-13B are diagrams of ingress paths that are blocked by acombination of a thin film encapsulation structure and a local glassseal.

FIGS. 14A-14B are diagrams of lens functions that may be performed by alocal glass seal.

FIG. 15 is a diagram of a local glass seal acting as an optical filter.

FIG. 16 is a diagram of a local glass seal performing a color shiftfunction.

FIG. 17 is a diagram of a local glass seal performing a scatteringfunction.

FIG. 18 is a diagram of a flexible electroluminescent panel having localglass seals.

FIG. 19 is a diagram of a sixth embodiment having local glass sealsbelow a thin film encapsulation layer.

FIG. 20 is a diagram showing a detail of an OLED element over a localglass seal.

FIGS. 21A-21F depict exemplary commercial products: a phone, a monitor,a television, a wristwatch, an OLED panel, and a luminaire,respectively.

FIGS. 22A-22E are conceptual representations of two-dimensional arraysof electro-optical elements.

FIGS. 23A-23E are conceptual representations of local encapsulationseals underneath respective two-dimensional arrays of electro-opticalelements.

FIGS. 24A-24G are diagrams of an electroluminescent panel at differentstages of formation of local glass seals.

FIG. 25 is a diagram showing components of an embodiment of a pre-formedencapsulation substrate, at an intermediate stage of manufacture.

FIG. 26 is a flow chart showing process steps for manufacture of apre-formed encapsulation substrate.

FIGS. 27A-27C are diagrams showing views of a single window element, andan embodiment of a pre-formed encapsulation substrate formed therefrom.

FIGS. 28A-28B are diagrams showing views of a pre-formed element, and anembodiment of an encapsulation substrate formed therefrom.

FIGS. 29A-29C are diagrams showing views of an electro-optical arrayassembly, a separate lower encapsulation substrate, and a panelassembled therefrom.

FIG. 30 is a flow chart showing process steps for manufacture of a panelfrom a pre-formed encapsulation substrate.

FIG. 31 is a diagram showing an embodiment of the invention havingtransparent local seals both above and below an array of electro-opticalelements.

DETAILED DESCRIPTION OF THE INVENTION

Electro-optical arrays are widely used in commercial products. FIGS.21A-21D show respectively a phone, a monitor, a television set, and awristwatch, all of which have pixel arrays used for information display.FIGS. 21E-21F show respectively an OLED lighting panel and an OLEDluminaire, both of which have arrays of OLED elements used forillumination.

By way of example, Company A may manufacture phone displays on a motherglass; following fabrication of display elements and encapsulation,singulation, and possibly other finishing steps such as assembly withcover layers, connectorization, and packaging, a large number of displaypanels or display modules are obtained. These display panels are furtherassembled into phones, either by Company A or by another company. Themanufacture of other display products of interest is similar, in that afinished display panel is incorporated into a finished product. Themanufacture of lighting products of interest is also similar, in that afinished lighting panel is incorporated into a finished product.Generally, electro-optical arrays are manufactured as panels, althoughsingulation from a mother substrate may not always be used. The skilledpractitioner will recognize that many manufacturing variations arepossible, and the steps described above are not necessary steps in theprocess of manufacturing a panel.

The term “panel product” is used to mean any product that is or thatincorporates a finished electro-optical panel. Thus, the termencompasses a wide range of display panels, lighting panels, otherelectro-optical panels, display products (such as television, phone,camera, monitor, wristwatch), lighting products (such as an OLEDluminaire). Not all phones are display products (for example, a rotarydial phone), and not all lighting products incorporate a finishedelectro-optical panel (for example, an incandescent light bulb). Also, amother substrate is not a panel product, because prior to singulationand finishing steps, it does not comprise a finished electro-opticalpanel. However, increasing numbers of display and lighting products doincorporate electro-optical panels (such as display panels and lightingpanels), and are panel products as understood in this disclosure.

Common features of electro-optical panels of interest in this disclosureinclude: a lower substrate, a two-dimensional array of electro-opticalelements formed over the lower substrate, and an upper structure,wherein the electro-optical elements are encapsulated between lowersubstrate and the upper structure. Of course, depending on thetechnology, application requirements, and particular design, embodimentswill have a varied range of additional features. Panels may be rigid orflexible.

In some embodiments, the upper structure may be a substrate, such as aglass substrate or a metal substrate. In some other embodiments, theupper structure may be a conformal coating, such as a thin-filmencapsulation comprising one or more layers. In still other embodiments,the upper structure may be a composite structure comprising one or morestrength members and one or more sheath layers. In some preferredembodiments, the upper structure is flexible.

The terms “lower” and “upper” refer to a conceptual order of manufacturefrom bottom to top—that is, active elements are formed over a bottomsubstrate, and a top substrate is applied later. Of course, the physicalorientation of the panel during manufacture and during use could becompletely different from the orientation implied by the terms “lower”and “upper”. In this disclosure, terms related to vertical order(including but not limited to “above”, “below”, “over”, “under”, “top”,“bottom”, “beneath”, “underneath”) likewise refer to the same conceptualorder of manufacture from bottom to top. Such terminology is common inthe art, where, for example, “bottom-emitting device” and “top-emittingdevice” are well understood by one of ordinary skill in the art.

FIG. 1 depicts a prior art electroluminescent device 100 havingencapsulation provided by an upper substrate 103. Light-emittingelements 104 are formed over a lower substrate 101. Customarily, theupper substrate 103 is attached to the lower substrate 101 using aperimeter seal 105. Thus, the encapsulation around light-emittingdevices is formed by lower substrate 101, perimeter seal 105, and uppersubstrate 103. Most commonly, both lower substrate 101 and the uppersubstrate 103 are formed of glass. The perimeter seal 105 may commonlybe a cured resin or a glass frit. The encapsulation defines a cavity 106that may be filled with dry nitrogen gas.

Between lower substrate 101 and light-emitting elements 104 there arecommonly intermediate layers variously including one or more of bufferlayers, planarization layers, dielectric layers, banks, passive wiringlayers, and active TFT layers: these are collectively represented inFIG. 1 by structure 102. Prior art device 100 may have additionalelements between the light-emitting elements 104 and upper substrate103. These additional elements are not shown in FIG. 1, but may includeone or more of top electrode interconnection, a protection layer, colorfilters, a black matrix, desiccant, and a scattering layer.

The device 100 may commonly be a top-emitter, in which case light isemitted through a transparent upper substrate 103, or a bottom-emitter,in which case light is emitted through transparent portions of structure102 and a transparent lower substrate 101.

FIG. 2 depicts a prior art electroluminescent device 200 havingencapsulation provided by an upper structure that is a thin filmencapsulation structure 201. Light-emitting elements 204A, 204B, 204Care formed over a lower substrate 101. Between lower substrate 101 andlight-emitting elements 204A, 204B, 204C there are commonly intermediatelayers variously including one or more of buffer layers, planarizationlayers, dielectric layers, banks, passive wiring layers, and active TFTlayers: these are collectively represented in FIG. 2 by lower structure202. Between light-emitting elements 204A, 204B, 204C and thin filmencapsulation structure 201 there may be an intermediate structure 203.Commonly, structure 203 comprises top electrode interconnection, but mayalso include other elements such as a protection layer, color filters, ablack matrix, desiccant, and a scattering layer.

The thin film encapsulation structure 201 may be attached to lowersubstrate 101 directly, as shown on the left-hand side of FIG. 2, orthrough structure 202 and/or structure 203, as shown on the right-handside of FIG. 2. Thus, the encapsulation around light-emitting devices204A, 204B, 204C is formed by lower substrate 101, thin filmencapsulation structure 201, and optionally structure 202 and/orstructure 203.

Different physical configurations are possible. Light emitting elements204A are shown being built substantially on top of structure 202, sothat the thin film encapsulation structure 201 fills in the gaps betweenlight-emitting elements 204A. Alternatively, light emitting elements204C may be formed in recesses in the structure 202, so that theunderside of the thin film encapsulation structure 201 overlight-emitting elements 204C is more smooth and/or more flat than theunderside of the thin film encapsulation structure 201 overlight-emitting elements 204A. As a further alternative, light-emittingelements 204B may be partially submerged in recesses in structure 202.While light-emitting elements 204A, 204B, 204C are depicted as havingrectangular cross-section, any of the surfaces may in fact be curved orslanted.

The device 200 may commonly be a top-emitter, in which case light isemitted through a transparent thin film encapsulation structure 201, ora bottom-emitter, in which case light is emitted through transparentportions of layers 202 and a transparent lower substrate 101.

First Embodiment

FIG. 3 depicts a first embodiment of the present invention. Panel 300comprises electro-optical elements 304R, 304G, 304B formed over a lowersubstrate 301. Electro-optical elements 304R, 304G, 304B are part of atwo-dimensional array of electro-optical elements 304 formed over thesubstrate 301. (Two-dimensional arrays of elements are discussedfurther, below, in context of FIG. 22.) Lower substrate 301 comprises amatrix 308 having light-transmissive local seals 305R, 305G, 305B formedas windows in the matrix 308. In preferred embodiments, and as shown inFIG. 3, each electro-optical element 304R, 304G, 304B has a respectivelocal seal 305R, 305G, 305B positioned directly below it. Between lowersubstrate 301 and electro-optical elements 304R, 304G, 304B there may beintermediate layers variously including one or more of buffer layers,planarization layers, dielectric layers, banks, passive wiring layers,and active TFT layers: these are collectively represented in FIG. 3 bystructure 302.

In preferred embodiments, lower substrate 301 may comprise a metal.Lower substrate 301 may comprise a single metal layer. Alternatively,lower substrate 301 may be a composite comprising a plurality of metallayers, or at least one metal layer and at least one non-metallic layer.

In preferred embodiments, local seals 305R, 305G, 305B, may comprise aglass material. Glass materials are particularly beneficial because theycombine low permeability with optical transmissivity. Glass materialsare known which are transparent, translucent, or opaque. In preferredembodiments, light emerges from the bottom of a panel through localseals such as 305R, 305G, 305B. As such, transparent and translucentglass materials are preferred. Additionally, as discussed further below,glass materials can be mixed, doped, or impregnated with additives andparticles to impart desired properties, such as optical filtering orscattering.

Individual electro-optical elements 304R, 304G, 304B are separated bybanks 303. The banks 303 may be formed integrally with structure 302 orseparately. The banks are shown extending in height above theelectro-optical elements 304R, 304G, 304B, which offers manufacturingadvantages in delineating the lateral boundaries of the electro-opticalelements 304R, 304G, 304B. Nevertheless, the bank height is not anecessary feature of the present invention. In some embodiments thetopmost extent of the bank may be lower than the top surface of localseals 304R, 304G, 304B. In other embodiments, banks 303 may bealtogether absent.

Similarly the presence of structure 302 is not a necessary feature ofthe present invention. In some embodiments, the functions of structure302 may be provided by a structure located beneath the lower substrate301. In other embodiments, structure 302 and lower substrate 301 may befabricated as an integrated unit.

In some preferred embodiments that incorporate a lower structure 302,lower structure 302 is light-transmissive. In other embodiments, lowerstructure 302 has light-transmissive portions. In some embodiments,light-transmissive portions of lower structure 302 are transparent. Insome embodiments, light-transmissive portions of lower structure 302 aretranslucent. In other preferred embodiments (not shown), lower structure302 is formed as a mesh having cutouts beneath each electro-opticalelement 304R, 304G, 304B. In such embodiments, lower structure 302 maybe opaque, translucent, or transparent. In some embodiments an opaquemesh lower structure 302 serves to reduce cross-coupling of lightbetween different pixels below the plane of the electro-optical elements304R, 304G, 304B. The opaque mesh lower structure 302 may be reflectiveor light-absorbing.

Above the banks 303 and electro-optical elements 304R, 304G, 304B liesupper substrate 309. In some embodiments upper substrate 309 is incontact with banks 303 at a set of discrete locations or a continuousset of locations. Accordingly, one or more upper regions 310 may bedefined above electro-optical elements 304R, 304G, 304B and betweenbanks 303. In some embodiments, upper regions 310 may comprise one ormore materials in common with bank 303. In other embodiments, upperregions 310 may comprise a thermally conductive material. In otherembodiments the one or more regions 310 may be filled with an inert gassuch as nitrogen, or a vacuum. In still other embodiments (not shown),the upper substrate 309 may conform to the surface of one or more banksand one or more electro-optical element 304R, 304G, 304B, therebyproviding direct contact between the one or more electro-optical element304R, 304G, 304B, and the upper substrate 309. In some embodiments,upper substrate 309 may be selected from materials having good thermalconductivity. In some embodiments, upper substrate 309 may be selectedfrom materials having good electrical conductivity.

In preferred embodiments, upper substrate 309 may comprise a metal.Upper substrate 309 may comprise a single metal layer. Alternatively,upper substrate 309 may be a composite comprising a plurality of metallayers, or at least one metal layer and at least one non-metallic layer.Some views of panel 300 in other figures omit the upper substrate 309.

In a preferred embodiment, each of electro-optical elements 304R, 304G,304B may be an organic electroluminescent element such as OLED (organiclight emitting diode) comprising an organic layer stack between a bottomelectrode and a top electrode. Some organic layer stacks, and methods ofmanufacture are described in U.S. Pat. Nos. 4,769,292, 5,904,961, and5,937,272. The organic layer stack may include an electroluminescentlayer as well as one or more of the following layers: a hole injectionlayer, a hole transport layer, an electron transport layer, and anelectron injection layer. Energy is released in the form of light duringelectron-hole recombination in the electroluminescent layer. Theelectroluminescent material may be a fluorescent material or aphosphorescent material. Additionally the OLED may have tandemstructure, in which case multiple OLED electroluminescent layers areseparated by powered or unpowered connectors, and light from a firstelectroluminescent layer passes through a second electroluminescentlayer before emerging from the light-emitting panel 300. Tandem OLEDstructures are described, for example, in U.S. Pat. No. 6,717,358 toLiao. As used herein, an organic layer stack has a plurality of layers,at least one layer of which comprises 50% or more by weight of one ormore organic compounds. As such, the organic layer stack may include oneor more layers comprising only inorganic material, such as LiF, or oneor more layer comprising an inorganic material as a minorityconstituent, such as a layer doped with metal atoms.

The present invention is not limited to organic electroluminescentelements. Electro-optical elements 304R, 304G, 304B may also be one ormore of the following: liquid crystal elements, inorganic light emittingdiodes (LEDs), quantum dot LEDs, electrochromic elements, inorganicelectroluminescent elements, thick film dielectric electroluminescentelements, plasma elements, field emission elements, electronic paper,interferometric modulator elements, surface conduction electron emitterelements, micromirror elements, and MEMS elements.

In a preferred first embodiment, panel 300 is an emissive display panel,and elements 304R, 304G, 304B emit red, green, and blue lightrespectively. Alternatively, panel 300 may be a transmissive,reflective, or transflective display panel. Panel 300 may further be alighting panel emitting fixed white light, temperature tunable whitelight, fixed colored light, or programmable colored light. Panel 300 mayalso be part of a transmissive product such as an electronic window, orsignage. Panel 300 may be substantially flat, or it may have perceptiblecurvature. Panel 300 may also be a component of a projection display.

In preferred embodiments panel 300 may be observed from the bottom.Light from elements 304R, 304G, 304B emerges through transparentportions of structure 302 and local seals 305R, 305G, 305B. In someembodiments, panel 300 may be observed from both top and bottom.

In many embodiments, each of electro-optical elements 304R, 304G, 304Bcomprise a bottom electrode and a top electrode, neither of which isshown in FIG. 3. The bottom electrode is directly connected to passivematrix or active matrix circuitry in lower structure 302. The topelectrode connection can be made in a variety of ways, not shown in FIG.3. In some embodiments, top electrodes are connected to each other overthe entire panel 300, i.e. the entire panel 300 has a common topelectrode. In other embodiments, top electrodes are connected to eachother in stripes which may be oriented along rows, columns, or diagonalsof the panel 300. The stripes may be straight, zigzag, or othersubstantially linear forms. In still other embodiments, the topelectrodes are connected to each other within each of a plurality oftwo-dimensional regions of the panel 300. Top electrode interconnectionsof any of these forms are routed above banks 303 in some embodiments orunder banks 303 in other embodiments. In still other embodiments, thetop electrode is connected locally at each element to circuitry withinthe structure 302.

As an example, element 304G is encapsulated by local seal 305G, matrix308, lower structure 302, bank 303, upper substrate 309, and optionallya top electrode interconnection. The encapsulation aroundelectro-optical elements 304R and 304B is similar.

Some embodiments may include additional upper elements between the topelectrode of an electro-optical element 304R, 304G, 304B and the uppersubstrate 309. Such elements may variously include one or more of: aprotection layer, a reflective layer, color filters, a black matrix,desiccant, and a scattering layer, according to the needs and design ofa particular embodiment. In some embodiments, one or more of theseadditional upper elements may extend beyond a single electro-opticalelement 304R, 304G, 304B, and therefore form part of the encapsulationsurrounding the corresponding electro-optical element 304R, 304G, 304B.These and other upper elements may take the form of an additionalstructure (not shown) above electro-optical elements 304R, 304G, 304Band below upper substrate 309, similar to structure 203 described incontext of FIG. 2.

It will be recognized that as the various components formingencapsulation around element 304G serve different functions, are formedof different materials by a variety of manufacturing processes, so thepermeation rates of moisture, oxygen, and/or other detrimental materialsthrough the various encapsulating components will not be the same. As ageneral rule, a thick layer of material offers a longer migration pathfor a detrimental material and a lower permeation rate, compared to athin layer of the same material. Additionally, electro-optical elements304R, 304G, 304B may have a functional area less than the physical area.

FIG. 20 shows a detail of an embodiment in which electro-optical element304M is an OLED element 304M having bottom electrode 2001 and a stack offunctional layers 2002. The area of contact between bottom electrode2001 and functional layer stack 2002 defines an active region 2003 ofthe OLED element. Moisture-sensitive material may extend laterallybeyond the active region 2003. In this case the lateral edges of theelectro-optical element 304M lie outside the functional area 2003, andtherefore penetration of oxygen, moisture, and/or other detrimentalmaterials to a lateral edge of electro-optical element 304M may haveless impact on product performance than penetration of the same amountof oxygen, moisture, and/or other detrimental material to the center ofthe electro-optical element 304M.

The functional layer stack 2002 may incorporate layers such as a holeinjection layer, a hole transport layer, an emissive layer, an electrontransport layer, an electron injection layer, and a cathode layer. Eachof these layers has a respective lateral extent, which may all be thesame in some embodiments, and some of which may be different in otherembodiments.

For reasons such as these, satisfactory encapsulation of element 304G(FIG. 3) or 304M (FIG. 20) can be achieved with a combination of thevarious components forming encapsulation around the element 304G or304M, despite considerable variation in the permeation rates through thematerials constituting the various encapsulating components.

In some embodiments, neighboring local seals 305R, 305G, 305B, provide abenefit of an optically transmissive and/or optically transparent sealunder respective electro-optical elements 304R, 304G, 304B. In someembodiments, the local seals 305R, 305G, 305B, provide a benefit of aglass seal without compromising deformability, flexibility, orunbreakability of the panel 300. While each individual local seal 305R,305G, 305B, is rigid, the areas between neighboring seals can flex morereadily.

In order to preserve flexibility of the finished product in differentdirections of flexing, it is desirable that rigid local seals beseparated in these directions by gaps comprising flexible material. Insome preferred embodiments restrict the size of each local encapsulationseal in all directions along the surface of the associated lowersubstrate. More specifically, if the lower substrate is laid outhorizontally flat and the size of the two-dimensional array ofelectro-optical elements along a direction D along the top surface ofthe substrate is A_(D), and the size of one local encapsulation seal inthe same direction is S_(D), then these preferred embodiments will, forall directions D, have the ratio S_(D)/A_(D) less than or equal to 1/5,preferably less than or equal to 1/10, commonly less than or equal 1/30,and often less than or equal to 1/100. Alternatively, the size of onelocal encapsulation seal, measured as area in the plane of the overlyingtwo-dimensional array of electro-optical elements, can be compared withthe area of the array of electro-optical elements. In someabove-mentioned preferred embodiments, the ratio of local encapsulationseal area to the area of the array of electro-optical elements will beless than or equal to 4%, preferably less than or equal to 1%, commonlyless than or equal to 0.11%, and often less than 0.01%. In someembodiments, the ratio of the maximum number of electro-optical elementsabove any one local encapsulation seal to the total number ofelectro-optical elements in the array of electro-optical elements isless than or equal to 4%, preferably less than or equal to 1%, commonlyless than or equal to 0.11%, and often less than 0.01%. Additionally, insome preferred embodiments, the local encapsulation seals will have anaspect ratio less than 3:1, preferably less than 2:1, more preferablyless than 1.5:1, and commonly less than 1.2:1. The “aspect ratio” isunderstood to mean the ratio of (1) the longest dimension of a localencapsulation seal measured parallel to the plane of the substrate, to(2) the shortest dimension of the same local encapsulation seal measuredin the same plane.

Panel 300 may be part of a commercial product such as a phone. FIG. 21Ashows a phone 2110, which incorporates a display having an activelight-emitting region 2117 comprising a two-dimensional array ofelectro-optical elements. Panel 300 may be part of a commercial productincorporating an information display monitor. FIG. 21B shows informationdisplay monitor 2126 that is an integral part of laptop computer 2128.The information display monitor 2126 has an active light-emitting regioncomprising a two-dimensional array 2127 of light-emitting elements.Panel 300 may be part of a television set. FIG. 21C shows a curvedtelevision 2130 incorporating an active display region 2137 having atwo-dimensional array of pixels. Panel 300 may be part of a wearableelectronics product such as a wristwatch. FIG. 21D shows a wristwatch2140 in which an active display region comprises a two-dimensional array2147 of pixels.

Second Embodiment

Turning now to FIG. 4A, panel 400 (shown in top view) is a preferredsecond embodiment of a lighting panel comprising light emitting elements404 separated by banks 303. Local seals 405 lie beneath eachlight-emitting element 404. The lighting panel may be part of a lightingfixture or other lighting product, either as a removable part or as anintegrally fabricated component. FIG. 21F, adapted from U.S. Pat. No.7,638,941 shows a ceiling-mount OLED chandelier 2160; each OLED panel2167 is a removable unit.

Each light-emitting element 404 has a respective local seal 405. Asshown, the local seals 405 are hexagonal and are arranged in a hexagonalpattern forming a two-dimensional array. Light-emitting elements 404 andlocal seals 405 are arranged in similar hexagonal patterns. Of course,other patterns are possible. For example, FIG. 21E, adapted from U.S.Pat. No. 6,870,196, shows an OLED lighting panel 2150 comprising arectangular array of polygonal lighting elements 2154 formed on a commonsubstrate 2151.

Section AA′ is shown in cross-sectional view in FIG. 4B. Each local seal405 is positioned beneath a respective light-emitting element 404 formedover substrate 301. Between lower substrate 301 and light-emittingelements 404 there may be intermediate layers variously including one ormore of buffer layers, planarization layers, dielectric layers, banks,passive wiring layers, and active TFT layers: these are collectivelyrepresented in FIG. 4B by structure 302. The banks 303 may be formedintegrally with structure 302 or separately.

In a preferred embodiment, each of light emitting elements 404 may be anorganic electroluminescent element such as OLED (organic light emittingdiode), as described above. However, the present invention is notlimited to organic electroluminescent elements.

Lighting panel 400 may emit fixed white light, temperature tunable whitelight, fixed colored light, programmable colored light, or a combinationof any of these. Lighting panel 400 may also combine a lighting functionwith other functions including but not limited to a window, a mirror, adisplay, and signage.

In preferred embodiments, lighting panel 400 may emit light from thebottom, in which case light from elements 304 emerges throughtransparent portions of structure 302 and local seals 405. Someembodiments of lighting panel 400 may emit light from both top andbottom.

Element 404 in FIG. 4B is encapsulated by local seal 405, matrix 308(matrix 308 and local seals 405 together comprising lower substrate301), structure 302, and bank 303, and upper substrate 309. Similar topanel 300 described above, panel 400 may also have top electrodeinterconnections (not shown) between light emitting elements 304, andmay also have additional upper elements (not shown) between lightemitting elements 304 and upper substrate 309. A top electrodeinterconnection and/or these additional upper elements may also formpart of the encapsulation surrounding light emitting element 304.

As previously described, satisfactory encapsulation of light emittingelement 404 can be achieved with a combination of the various componentsforming encapsulation around the element 404, despite considerablevariation in the permeation rates through the materials constituting thevarious encapsulating components.

It is not necessary for each individual electro-optical element orlight-emitting element to have its own independent local seal in orderto realize the benefits of the present invention. FIG. 5 shows a thirdembodiment of a panel 500 wherein the area of each local seal 505A, 505Bencompasses the area of a respective group of electro-optical elements504A, 504B. The individual elements 504A are mutually separated by banks506, while a group of elements 504A is separated from a neighboringgroup of elements 504B by a bank 503. In preferred embodiments, theheight of bank 506 is less than the height of bank 503, but this is notnecessary. Between lower substrate 301 and elements 504A, 504B liesoptional structure 302, providing the same or similar functions asdescribed above. Upper substrate 309 is located above banks 503, 506 andabove pixel elements 504A, 504B. Between upper substrate 309 andelements 504A, 504B are one or more defined regions 310. Regions 310 andupper substrate 309 have already been described in context of FIG. 3.

Flexibility

FIG. 18 shows a bottom view of a curved or flexed panel 1800 utilizinglocal seals 1805 under electro-optical elements (not shown) formed onsubstrate 1801. Panel 1800 may be part of a display product, a lightingproduct, or any other product including but not limited to thosedescribed above in context of panels 300 and 400. It should beemphasized that FIG. 18 is not drawn to scale, because of the widelydisparate dimensions of the features shown. At the time of writing, OLEDdisplays are known with pixel sizes on the order of tens of microns. Bycomparison, requirements for bending radius may be on the order ofhundreds of microns for an unbreakable display, centimeters for abendable display, and meters for a curved television set. In someembodiments, the ratio of the largest transverse dimension of a localseal 1805 to the required bend radius will preferably not exceed 10%, ormore preferably 5%. Thus, depending on the bending requirements of aproduct, and the size and spacing of electro-optical elements, it may bepossible to accommodate varying numbers of electro-optical elementsabove each local seal 1805.

In some embodiments, local seals 1805 are made of glass, or anotherrigid material, while flexible substrate 1801 is less rigid and is ableto flex. When a sheet of material is bent, there may be elasticdeformation: one surface of the sheet experiences tension and isstretched, while an opposite surface of the sheet experiencescompression and is compressed. (Between the surfaces lies a neutralplane, which by definition experiences neither tension nor compressionas the sheet is bent.) The bending can be represented in geometricalterms as the local strain in the sheet. In the context of FIG. 18, theareas of panel 1800 where rigid local seals 1805 are located are stiffand undergo minimal deformation, and consequently have a low value ofstrain when the panel 1800 is flexed. In comparison, areas betweenneighboring local seals 1805 are flexible and undergo more deformation,leading to higher values of strain when the panel 1800 is flexed. Inembodiments of this invention having local seals 1805 made of glass, itis expected under flexion that the ratio of strain midway between afirst and a second neighboring local seals 1805 to the strain at aposition of the substrate lying beneath the center of either the firstor the second neighboring local seals is at least 2:1, usually at least5:1, commonly at least 10:1, and sometimes greater than or equal to20:1. In order to maximize the flexibility of such an embodiment, itwill be clear to the skilled practitioner that gaps between pixelsshould be left free to flex. That is to say, it is usually preferable tohave separate local encapsulation seals for each electro-optical elementin order to maximize flexibility. Exceptions may occur in cases wherepixels are of different sizes: grouping of smaller pixels over oneencapsulation seal may sometimes be performed without compromising theoverall flexibility of the two-dimensional array. The array 2250 shownin FIG. 23E provides one such example.

Patterns of Electro-Optical Elements and Local Seals

Returning to FIG. 5, panel 500 may be part of a display product, alighting product, or any other product including but not limited tothose described above in context of panels 300 and 400. As an example,in a display product, the three elements 504A may comprise a red pixel,a green pixel, and a blue pixel. In a display product havingfour-element pixel groups, such as RGBG or RGBW—where the letters R, G,B, and W respectively denote red, green, blue, and whiteelements—elements of 504A may comprise two, four, or some other numberof elements, from the same or different pixel groups. In a lightingproduct having a hexagonal layout of lighting elements similar to thelayout shown in FIG. 4A, groups of elements 504A to be covered by acommon local seal may be diamond-shaped groups of four elements, orhexagonal-shaped groups of seven elements. Many other groupings ofelements are also possible within the scope of this third embodiment.

FIG. 22 shows some possible arrangements of electro-optical elements ina two-dimensional array. FIG. 22 is only a conceptual representation ofelectro-optical elements; the other features of product embodiments suchas a substrate, local seals, and banks are not shown. The full extent ofa typical two-dimensional array is not shown either. FIG. 22A shows arectangular array 2210 of stripe elements 2214. FIG. 22B shows arectangular array 2220 of circular elements 2224. FIG. 22C shows arotated rectangular pattern 2230 of rectangular- and oval-shapedelements 2234A, 2234B, 2234C, 2234D similar to the pattern found in someSamsung Galaxy™ phones. FIG. 22D shows a hexagonal pattern 2240 ofcircular elements 2244. FIG. 22E shows a rectangular pattern 2250 ofdifferent shaped elements 2254A, 2254B, 2254C arranged in blocks. Itwill be understood by a skilled practitioner that the various featuresof these patterns may be combined in numerous combinations, and thatmany other patterns are also possible. The elements in FIGS. 22A-22E maybe OLED elements, display pixels, electrophoretic elements, or othersuch electro-optical elements as are described elsewhere in thisdisclosure. In some preferred embodiments, all local encapsulation sealshave the same size and shape.

FIGS. 23A-23E show bottom views of some possible arrangements of localencapsulation seals for the patterns of FIG. 22. Dotted lines representelectro-optical elements that lie above these seals. Once again, FIG. 23contains conceptual representations only; local encapsulation seals ofdifferent shapes and sizes are shown together as a matter ofconvenience. As the skilled practitioner will recognize, it is to beexpected that within one embodiment, substantially all of the localencapsulation seals will be the same size and shape, with possibleexceptions near edges of the overlying two-dimensional array ofelectro-optical elements. Likewise, it is to be expected that eachelectro-optical elements of the two-dimensional array will be coveredfrom below by a local encapsulation seal. Of course, it is usuallypossible to arrange local encapsulation seals so that each local sealcovers exactly one electro-optical element, as shown by localencapsulation seals 2315C, 2325A, 2335A-2335D, 2345A, and 2355A-2355C incorresponding FIGS. 23A-23E. As discussed above, for embodiments havingrigid local seals, embodiments having distinct local seals for eachelectro-optical element of the two-dimensional array will generallymaximize the flexibility of the sealed array.

The other encapsulation seals 2315A-2315B, 2325B-2325C, 2335E-2335F,2345B-2345D, and 2355D-2355F indicate some possible configurationswhereby electro-optical elements can be grouped in the correspondingtwo-dimensional arrays of FIGS. 23A-23E, with one local encapsulationseal under each group. These configurations are suitable for embodimentsin which the substrate and local seals have comparable stiffness, orembodiments in which flexibility does not need to be maximized. Becausethere are lateral permeation pathways from the edge of a local seal toan overlying electro-optical element, configurations with grouped localseals provide less total seal perimeter and, on average, longerpermeation pathways compared to configurations having distinct localseals for each pixel. That is to say, grouping electro-optical elementsover a common local encapsulation seal is effective to achieve lowerpermeation rates.

Manufacture

FIGS. 6A-6F depict sequential manufacture of the local seals of arepresentative embodiment of this invention. FIG. 6A shows an unfinishedpanel 600 prior to formation of any local seal. Electro-optical element304, which is an OLED element in certain preferred embodiments, has beenformed over a starter substrate 608 and lower structure 302, describedabove. Banks 303 surround electro-optical element 304 and separate thiselement from neighboring electro-optical elements (not shown in FIG.6A-6F).

In preferred embodiments, the starter substrate 608 may be opaque. Asdiscussed previously, lower structure 302 may be wholly or partiallylight-transmissive. The objective of the manufacturing process is toprovide a plurality of light-transmissive sealed windows in the startersubstrate 608, so that light can pass through the layers beneathelectro-optical element 304 and exit the panel. For the sake of clarity,FIGS. 6A-6F depict formation of a single local seal; it will be evidentto the skilled practitioner that each step can be replicated for each ofa plurality of local seals. Some steps, such as an etching step, areamenable to simultaneous performance for a plurality of window openings.Other steps, such as an inkjet deposition step, are amenable tosequential performance for each of a plurality of local seals. Stillother steps, such as fusing glass powder by a laser, are amenable tosequential performance for one group of local seals at a time.

FIG. 6A is drawn showing the lower substrate on the bottom of thedrawing, for consistency with other figures and conventionalnomenclature for e.g. “upper”, “lower” as discussed previously. It willbe apparent to one or ordinary skill in the art that during themanufacturing process, the panel being manufactured can be held in anyorientation, and can be shifted from one orientation to another betweenprocess steps and even during process steps. Accordingly, FIGS. 6A-6Fare drawn with unfinished panel 600 shown in the same orientation sothat the manufacturing steps are easier to follow, and it will beunderstood that one or another orientation may be preferred for anyindividual process step.

FIG. 6B shows formation of a dam 603 around a target area for a windowbelow electro-optical element 304. Dam 603 below may be formed by aphotolithographic process or a screen printing process, both of whichare well-known in the art. As shown in FIG. 6B, dam 603 is a narrowannulus, local to one electro-optical element, which has an advantage oflower material usage. Alternatively dam 603 may be pre-formed as a maskextending over the area of a group of electro-optical elements, or evenover the entire active area of the panel 600, with cutouts for aplurality of electro-optical elements. In such embodiments, the dam 603may have a shape and extent comparable to bank 303.

Exemplary materials suitable for formation of dam 603 include metal etchresists. A number of suitable products are available. For example,Nazdar Alkali Removable Etch Resist Ink 226 Black is available from fromNazdar Ink Technologies, Shawnee, Kans.

FIG. 6C shows a cutout having been etched in the target area for sealformation below electro-optical element 304. Thereby starter substrate608 shown in FIGS. 6A-6B is now a matrix 308, having openings beneatheach electro-optical element 304. In preferred embodiments, startersubstrate 608 comprises metal. A wide variety of chemical etchants areknown for removing metals, including ferric chloride solution, copperchloride solution in aqueous hydrochloric acid, aqueous acid solutionssuch as nitric acid or hydrochloric acid, aqueous acid mixtures such asphosphoric acid+nitric acid+acetic acid, and some proprietary etchants.Some metals such as aluminum can also be dissolved in alkaline solutionssuch as sodium or potassium hydroxide. Chemical etching is preferred, asetchants can readily be chosen that do not attack the material of lowerstructure 302, which may be a polymer. Alternatively, etching can beperformed by other known technologies, including plasma etching andlaser ablation.

FIG. 6D shows deposition of a glass powder paste 602 onto element 304 bya nozzle 601. For this process step, it may be preferred to haveunfinished panel upside-down, so that glass powder paste 602 can be heldin place by gravity. However an upside-down orientation is notessential, as the glass powder paste 602 may have sufficient adhesion tothe exposed lower surface of lower structure 302 and the slant walls ofmatrix 308 to provide support for a thin film of the glass powder paste602. This deposition technique is often referred to informally as inkjetmaterial deposition, or inkjet printing. While paste 602 is shown havingan uneven bottom surface, in practice this bottom surface will be moreor less smooth according to the viscosity and surface tension of thedeposited formulation, and the force of ejection from nozzle 601. Nozzle601 is part of an inkjet dispenser. In some embodiments, nozzle 601 mayplace one or more droplets of glass powder paste in a first opening,followed by one or more droplets of glass powder paste in a secondopening. In some embodiments the second opening may be a neighbor of thefirst opening; in other embodiments, a plurality of inkjet dispensersand/or more complicated traversal algorithms may be used.

FIG. 6E shows curing of the glass powder paste by irradiation 606 from alaser beam source 604. At this stage, the glass powder paste 602 hasmelted, the carrier material of the glass powder paste has volatilized,and the glass powder particles have fused into a liquid mass 607 that isadhered to the slant walls of matrix 308 and the bottom surface of thelower structure 302. In embodiments having either no lower structure orcutouts in lower structure 302, the liquid mass 607 may be adhereddirectly to a bottom surface of electro-optical element 304, which maybe a bottom electrode surface. The liquid mass 607 has a smooth surfaceas shown.

Finally, FIG. 6F shows the cured local glass seal 305 after it hascooled and hardened, and after dam 603 has been removed. Matrix 308 andlocal seal 305 comprise lower substrate 301. In order that matrix 308and local seal 305 form a continuous seal, it is desirable that localseal 305 is adhered to matrix 308. Local seal 305 may also be adhered tolower structure 302. In some embodiments, local seal 305 mayadditionally or alternatively be adhered to a bottom surface ofelectro-optical element 304. It will be recognized that the structure ofFIG. 6F resembles the structures previously shown in FIGS. 3-5, and thatthis manufacturing method is generally applicable to a wide variety ofembodiments of this invention including but not limited to thosedescribed above.

The step of dam removal is not essential to the practice of thisinvention. In some embodiments, dam 603 is left in place after formationof local seal 305. In such applications, a suitable material for dam 603is Nazdar ADE Series Epoxy Screen Ink.

In particular, one of ordinary skill in the art will recognize that thelayers above lower structure 302 each play a minimal role in themanufacturing process shown in FIGS. 6A-6F. Thus, while it is possibleto fabricate local seals 305 after the electro-optical elements andbanks have been formed, as described above, it is also possible, and maybe preferable to form the local seals 305 before forming electro-opticalelements 304, and even before forming banks 303. In preferredembodiments, banks 303 and dams 603 are formed on opposite sides ofstarter substrate 608, then local seals 305 are formed, thenelectro-optical elements 304 are formed, and finally upper structure andupper substrate are assembled (not shown in FIGS. 6A-6F), producing anencapsulated panel.

It will further be recognized that the manufacturing method described isexemplary, and numerous variations are possible without departing fromthe spirit and scope of this invention. Depending on the size of localseal being formed and the construction of lower substrate 301 and lowerstructure 302, techniques such as screen printing and electrophoreticdeposition may particularly be suitable. Further, after completion ofmanufacture, unfinished panel 600 may result in a finished product thatcould be a display product, a lighting product, or any other productincluding but not limited to those described above in context of panels300 and 400.

While, in preferred embodiments, the local seals are formed of glassusing a glass powder paste or suspension, the invention is not solimited. In other embodiments, local seals may be formed from organicresins, inorganic compounds, eutectic metal alloys, or other metals.

The seal material may be deposited as a powder, paste, suspension,solution, or in integral form (that is, as a pre-formed solid seal to befused to one or more underlying structures) under the electro-opticalelements 304. The deposition process may use inkjet technology, physicalvapor deposition, chemical vapor deposition, printing, sputtering,powder coating, electroplating, electroless plating, and plasma coating.Patterning of the deposited material according to the desired localseals may be done at the time of deposition or subsequently.

Curing of the seal material may be performed by thermal means, such ashot gas, convection, or electrical heating. Electrical heating may takeforms including but not limited to induction, resistive, dielectric, RF,and microwave heating. Curing may be performed by external radiation,including infrared lamps, ultraviolet lamps, or laser. Curing may beperformed chemically, as in the case of two-part epoxies. Forembodiments using heat in the curing process and having organicconstituents within electro-optical elements 304, and particularly forpreferred embodiments having elements 304 that are OLED elements, thetemperature of the local encapsulation seals, the elements 304, and thesubstrate may be controlled to be less than or equal to 300° C.,preferably less than or equal to 275° C., commonly less than or equal to250° C., and sometimes less than or equal to 225° C. Of course, curingtemperature is much less of a concern in embodiments where OLED elementsare formed after formation of local encapsulation seals.

FIGS. 7A-7C show some configurations for curing the local seals 607using heat and radiation. As discussed above, the orientation ofunfinished panel in FIGS. 7A-7C is shown consistently with other figuresand as a matter of convention, and may differ from the actualorientation of unfinished panel 600 for a particular process step. FIG.7A shows a furnace 701 in which the entire unfinished panel 600 is beingheated. In some embodiments the space 702 inside the furnace 701 isfilled with a gas such as dry nitrogen. In other embodiments, the space702 is evacuated to a pressure lower than atmospheric pressure, or avacuum, and unfinished panel 600 is heated by infrared radiation fromhot walls of the furnace 701 or from heat lamps (not shown) installed inthe furnace 701. Transport of the unfinished panel 600 in and out of thefurnace 701 may be accomplished in some embodiments by continuoustransport, in a form of a conveyor belt or in an equivalent form.Transport may also be accomplished on a cyclical basis as sequence ofdiscrete steps: open furnace door, introduce unfinished panel 600 withuncured local sealing material, close furnace door, apply heat to curethe local sealing material, open furnace door, extract panel 600 withcured local seals.

FIG. 7B shows an embodiment for heating just the bottom of unfinishedpanel 600. The unfinished panel 600 is held by suction cups 705 andtransported through a heating zone by a suspended conveyor arrangementincluding rollers 706 and track 712. One or more radiation sources 703provide irradiation 704 of only the bottom surface of unfinished panel600, which results in curing of the seal material 607. It will berecognized that heating of just the bottom surface need not be performedusing continuous transport, but can also be performed in a heatingchamber similar to furnace 701 having, for example, heat lamps installedin a bottom wall only.

FIG. 7B shows unfinished panel 600 without either banks 303 orelectro-optical elements 304. Thus the entire substantially planar topsurface of lower structure 302 is available for holding the unfinishedpanel 600, either by suction cups 705 as shown or another fasteningmechanism. One of ordinary skill in the art will also recognize that ifunfinished panel 600 is held upside-down, then an ordinary conveyorsystem (with rollers contacting the exposed surface of lower structure302) is quite satisfactory, and there is no need for the suspendedconveyor as shown.

FIG. 7C shows an embodiment for sequential heat curing of local seals305, 607, 602 using irradiation from laser source 707. Unfinished panel600 is located upside-down beneath the laser source 707. Irradiation 708from the laser is in the form of a conical beam 709 and irradiates aspot 710 that encompasses a single local seal 607, causing this seal tobe heated and cured. Arrows 711 indicate that the laser is scanned intwo dimensions (preferably in steps, from one local seal to another) tosuccessively heat and cure all the local seals being formed onunfinished panel 600. As indicated, some local seals labeled 602 haveyet to be cured. Other local seals labeled 305 have already been cured.It will be recognized that although arrows 711 are shown next to thelaser source 707, the translation can alternatively be applied to theunfinished panel 600. In some embodiments, one axis of translation isperformed by moving the laser beam, while another axis of translation isperformed by moving the unfinished panel 600.

The embodiments described above in context of FIGS. 7B and 7C have anadvantage of using less total heat energy compared to the embodimentdescribed above in context of FIG. 7A. This has numerous benefits,including but not limited to less energy cost, less cooling time, lowerTACT time, higher manufacturing throughput, and reduced heat damage tothe unfinished product 600.

It will be recognized that laser beams can have a variety of tailoredbeam profiles, some of which are shown in FIGS. 8A-8C. FIG. 8A shows aspot beam profile illuminating a local seal 607. Graph 801 representsthe beam profile along cross-section AA′. The axes of the graph are I,the intensity of irradiation, a quantity which may be measured in W/cm²,and x, which is the distance coordinate along the AA′ section. Graph 802represents the beam profile along cross-section BB′. I is the intensityof irradiation, and y is the distance coordinate along the BB′ section.

FIG. 8B shows a multi-spot beam illuminating several of the local seals607. Graphs 803 and 804 show the beam profiles along cross-sections AA′and BB′. In the example shown, the laser beam has two spots, each ofwhich illuminates two neighboring local seals 607. Of course, othercombinations are possible, such as five spots illuminating one localseal each, or one spot illuminating four neighboring local seals: two ineach of two neighboring rows.

FIG. 8C shows a linear beam illuminating a row of local seals 607.Graphs 805 and 806 show the beam profiles along cross-sections AA′ andBB′. Of course, other arrangements are possible, such as a beamilluminating two rows of local seals, or a beam having width along theBB′ cross-section that is narrower than the width of the local seals607. In the latter arrangement, the laser beam is scanned back and forthin they direction to provide irradiation and heating of the entire areaof the local seals 607.

As described above, the encapsulation of an electro-optical element suchas 304, 304R, 304G, 304B, 504A, 504B is comprised of a number ofcomponents having varying material composition and varying permeationrates for moisture, oxygen, and/or other detrimental materials. Althougha local seal such as a local glass seal may provide adequate sealingover the bottom surface of an overlying electro-optical element, sidepaths through other encapsulating components may adversely affectproduct performance and lifetime. For this reason, it may be desirablein some applications to combine a local seal with a thin filmencapsulation structure. In some panel embodiments, such a supplementarythin film encapsulation structure extends across and even beyond theextent of the active region of the panel.

Combination of Local Seals with Thin Film Encapsulation

FIG. 9 shows a fourth embodiment of the present invention. Lowersubstrate 301, intermediate layer structure 302, banks 303,electro-optical elements 304, and local seals 305 are substantiallysimilar to the corresponding elements described in context of FIG. 3above, and may be manufactured by similar processes. The fourthembodiment adds a thin film encapsulation structure 901 below the localseals 305 and matrix 308. The thin film encapsulation structure 901 maybe a single layer, or may be a composite of multiple layers. Panel 900may be part of a display product, a lighting product, or any otherproduct including but not limited to those described above in context ofpanels 300 and 400.

Some embodiments may include additional upper elements between the localseal 305 and the thin film encapsulation structure 901. Such elementsmay variously include one or more of: a protection layer, color filters,a black matrix, desiccant, and a scattering layer, according to theneeds and design of a particular embodiment. In some embodiments, one ormore of these additional upper elements may extend beyond a single localseal 305 and therefore form part of the encapsulation surrounding acorresponding electro-optical element 304.

Panel 900 can be manufactured by a process very similar to thatdescribed above using FIGS. 6A-6F. An additional step is performed afterthe step of FIG. 6E, to laminate a conforming thin film encapsulationstructure onto the bottom surface of matrix 308 and local encapsulationseals 305. This step can be performed after removal of dam 603, or itcan be performed without removal of dam 603.

FIG. 10 is a flow chart showing some manufacturing steps for a panelaccording to an embodiment of FIG. 9. At step 1001, a starter substrateis formed. At step 1002, a lower structure is formed over the startersubstrate. At step 1003 local seals 305 are formed. Step 1003 may beperformed by a variety of methods including but not limited to thosedescribed in context of FIGS. 6-7 above. At step 1004, thin filmencapsulation structure 901 is formed.

Not shown in FIG. 10 are the steps of forming electro-optical elements304, an upper structure, and providing top encapsulation with uppersubstrate 309. The step of forming electro-optical elements can beperformed between steps 1002 and 1003, in accordance with the embodimentof FIGS. 6A-6F, which show manufacture of local seals 305 withelectro-optical elements 304 already in place. Alternatively, the stepof forming the electro-optical elements 304 can be performed after step1003, in accordance with FIG. 7C, where the process of forming localseals 305 is being completed prior to fabrication of electro-opticalelements 304. Likewise, the step of providing top encapsulation can beperformed before or after step 1004. A step of forming an upperstructure can be performed at any point after fabrication ofelectro-optical elements and before provision of top encapsulation.

FIG. 13A shows how the combination of a local seal 305C, 305D with athin film encapsulation structure 901 provides advantages. Panel 900 hasstructure substantially similar to that shown in FIG. 9. In this figure,dotted line 1301 denotes a pinhole defect in the thin film encapsulationstructure 901. Were it not for the local seal 305C, oxygen, moisture,and/or other detrimental materials could penetrate through pinholedefect 1301 and damage the electro-optical element 304C above. In thepresent embodiment, penetration through the thin film encapsulationstructure 901 can proceed as shown by arrow 1302. However seal 305Cprevents further penetration as indicated by the X on arrow 1303. Arrow1304 represents permeation through lower structure 302. In flexiblepanels lower structure 302 may comprise a flexible material, such as apolymer, that by itself provides inadequate resistance to penetration ofoxygen, moisture, and/or other detrimental materials. Consequently thereis no X on arrow 1304.

Turning now to electro-optical element 304D, dotted line 1305 representsa pinhole path for migration of moisture, oxygen, and/or otherdetrimental materials through matrix 308. Alternatively, such a pinholepath may exist at the interface between matrix 308 and local seal 305D.Were it not for thin film encapsulation structure 901, moisture, oxygen,and/or other detrimental materials could penetrate through the pinholepath 1305 and lower structure 302, as shown by arrows 1307 and 1308respectively, to contaminate the sensitive electro-optical element 304D.In the present embodiment, however, the thin film encapsulationstructure 901 blocks this path, as shown by the X over arrow 1306, anddegradation of electro-optical element 304D is prevented.

FIG. 11 shows a fifth embodiment of the present invention. Like thefourth embodiment described above in context of FIG. 9, the fifthembodiment adds a thin film encapsulation structure 1101 to the basicstructure described in context of FIG. 3. However, in this case, thethin film encapsulation structure 1101 lies over the local seal 305. Inother respects thin film encapsulation structure 1101 is similar topreviously described thin film encapsulation structure 901. Otherwise,panel 1100 is substantially similar to panel 900.

FIG. 24A-24G depict sequential manufacture of the local seals of anembodiment of this invention similar to the embodiment of FIG. 11. Forthe sake of clarity, FIGS. 24A-24G depict formation of a single localseal; it will be evident to the skilled practitioner that each step canbe replicated for each of a plurality of local seals. Unlike FIGS.6A-6F, FIGS. 24A-24G show formation of a local seal prior to fabricationof any electro-optical elements above lower structure 302, and alsobefore formation of banks 303. Several other details of FIGS. 24A-24Gand their associated steps are similar to those of FIGS. 6A-6F, and arenot repeated here.

FIG. 24A shows an unfinished panel 240 prior to formation of any localseal. Starter substrate 608 and lower structure 302 have been assembled.FIG. 24B shows an annular dam 603 formed around a target area for awindow. FIG. 24C shows a cutout having been etched in the target areafor seal formation. Due to etching of one or more cutouts, startersubstrate 608 has become matrix 308. FIG. 24D shows thin filmencapsulation structure 1101 formed on the lower surface of theunfinished panel 240. FIG. 24E shows deposition of a glass powder paste602 into the partially filled cutout by a nozzle assembly 601. FIG. 24Fshows curing of the glass powder paste by irradiation 606 from a laserbeam source 604. At this stage, the glass powder paste 602 has melted,the carrier material of the glass powder paste has volatilized, and theglass powder particles have fused into a liquid mass 607 that is adheredto thin film encapsulation structure 1101 in the cutout region. Finally,FIG. 24G shows the cured local glass seal 305 after it has cooled andhardened. In this embodiment, dam 603 is not removed. The skilledpractitioner will understand that the location of each local seal ischosen according to a pattern of electro-optical elements in a finishedproduct formed from unfinished panel 240. In some embodiments, exactlyone electro-optical element is formed directly above each local seal305. In other embodiments, a plurality of electro-optical elements mayshare a single local seal 305.

It will be recognized that there are pathways for permeation that gothrough encapsulation structure 1101 but do not pass through any oflocal seals 305. However, as with other figures, FIG. 11 is not toscale. In particular, the thicknesses of the features shown are greatlymagnified in comparison to the transverse extents. Therefore, a pathwaythrough encapsulation structure 1101 that bypasses 305 is very narrowand relatively long. By comparison, in the absence of local seals 305, apathway directly through encapsulation structure 1101 and into thebottom of electro-optical element 304 would be very wide (essentiallythe full-width of element of 304) and very short (simply the thicknessof encapsulation structure 1101). By blocking a short, wide permeationpathway, the local seals 305 thus greatly improve the encapsulation ofpanel 1100.

It is not necessary for the local seal 305 to lie within a recess belowelectro-optical element 304. FIG. 19 shows panel 1900, which is a sixthembodiment. As in FIG. 11, thin film encapsulation structure 1901 isformed below elements 304J, 304K, 304L, and lies above local seals 305J,305K. However, in the sixth embodiment, structure 1901 acts as aplanarization layer, and the locals seals 305J, 305K are formedsubstantially or entirely below structure 1901, as shown. Local seal305J is shown formed below a single electro-optical element 304J.Alternatively, 305K is shown formed below a group of electro-opticalelements 304K, 304L. In other respects, panel 1900 is substantiallysimilar to panel 1100.

FIG. 12 is a flow chart showing some manufacturing steps for a panelaccording to an embodiment of FIG. 11. At step 1201, a starter substrateis formed. At step 1202, a lower structure is formed over the startersubstrate. At step 1203, thin film encapsulation structure 1101 isformed. At step 1204, local seals 305 are formed. Step 1204 may beperformed by a variety of methods including but not limited to thosedescribed in context of FIGS. 6-7 above.

As discussed above for FIG. 10, the steps of forming electro-opticalelements 304, an upper structure, and providing top encapsulation withupper substrate 309 are also not shown in FIG. 12. Further, it will bereadily understood that each step shown in FIGS. 10 and 12 may inpractice involve a plurality of smaller steps.

FIG. 13B shows how the combination of a local seal 305 with a thin filmencapsulation structure 1101 provides advantages. Panel 1100 hasstructure substantially similar to that shown in FIG. 11. In thisfigure, dotted line 1311 denotes a pinhole defect in the thin filmencapsulation structure 1101. Were it not for the local seal 305C,oxygen, moisture, and/or other detrimental materials could penetratethrough pinhole defect 1311, as shown by arrow 1313, and damage theelectro-optical element 304B above. However, in the present embodiment,seal 305B prevents access to the pinhole defect, as shown by the X onarrow 1312. Arrow 1314 represents permeation through lower structure302. In flexible panels, lower structure 302 may comprise a flexiblematerial, such as a polymer, that by itself provides inadequateresistance to penetration of oxygen, moisture, and/or other detrimentalmaterials. Consequently there is no X on arrow 1314.

Turning now to electro-optical element 304D, dotted line 1315 representsa pinhole path for migration of moisture, oxygen, and/or otherdetrimental materials through matrix 308. Were it not for thin filmencapsulation structure 1101, moisture, oxygen, and/or other detrimentalmaterials could penetrate through the pinhole path 1315 and lowerstructure 302, as shown by arrows 1317 and 1318 respectively, tocontaminate the sensitive electro-optical element 304D. In the presentembodiment, however, the thin film encapsulation structure 1101 blocksthis path, as shown by the X over arrow 1316, and degradation ofelectro-optical element 304D is prevented.

Optical Functions of Local Seals

In preferred embodiments, light emerges from electro-optical elementsthrough the corresponding local seals. As such, optical properties ofthe local seals can affect the emitted light. Therefore it may beadvantageous to customize optical properties of the local seals toachieve desired properties of emitted light. Optical functions that canbe designed into a local seal include but are not limited to a lensfunction, a filter function, and a scattering function.

FIG. 14A shows a panel 300, which in most respects is unchanged from thepanel previously described in context of FIG. 3. For the sake ofclarity, some elements such as encapsulating upper substrate are notshown. In this figure, local seals 305A, 305C, 305D lie beneathelectro-optical elements 304A, 304C, 304D respectively. Local seals305A, 305C, 305D are shown with different exemplary shapes, wherebydifferent lens functions can be achieved. Local seal 305A has top andbottom surfaces that are substantially plane and parallel, ray 1402exits the bottom surface of local seal 305A at the same angle that itwould have in the absence of local seal 305A. Thus, no lens function isobtained, which may be desirable for some products. Note that there maybe a small lateral shift of ray 1402 with respect to its direction ofpropagation, this is not consequential to the lens function and is notshown for ray 1402.

Turning now to local seal 305C, it can be seen to have a plano-convexshape, and an optical axis 1401. In the usual case where the medium(such as glass) inside local seal 305C has a higher refractive indexthan the medium (such as air) below the convex lower surface of thelocal seal 305C, the plano-convex local seal 305C acts as a converginglens. In comparison to ray 1403 incident at the top surface of localseal 305C, the emergent ray 1404 is bent away from the normal to thesurface, which produces the converging effect shown. The convergingeffect may be beneficial in display embodiments with regard to privacy.It will be recognized that such a lens function is not limited todisplay embodiments. Particularly, the converging effect may bebeneficial in lighting embodiments where spotlight illumination isdesired.

Local seal 305D is seen to have a plano-concave shape. In the usual casewhere the medium (such as glass) inside local seal 305D has a higherrefractive index than the medium (such as air) below the convex uppersurface of the local seal 305D, the plano-concave local seal 305D actsas a diverging lens. In comparison to ray 1405 incident at the topsurface of local seal 305D, the emergent ray 1406 is bent away from thenormal to the surface, which for the concave surface produces thediverging effect shown. The diverging effect may be beneficial indisplay embodiments where wide viewing angle is desired. The divergingeffect may be beneficial in lighting embodiments where omni-directionalillumination is sought.

FIG. 14B shows an alternate construction for lensed embodiments, inwhich plano-convex local seals 305 are covered with a planarizationlayer 1407. In this figure, local seals 305E, 305F, 305H lie beneathelectro-optical elements 304E, 304F, 304H respectively. The diagram forlocal seal 305F shows a case where the refractive index of the localseal 305F is greater than the refractive index of the planarizationlayer 1407. In this situation, local seal 305F provides a convergingeffect substantially similar to the converging effect seen for localseal 305B in FIG. 14A. In contrast, the diagram for local seal 305Hshows a case where the refractive index of the planarization layer isgreater than the refractive index of the local seal 305H. In this case,the diverging effect of a plano-concave lens defined by the top andbottom surfaces of the planarization layer is stronger than theconverging effect of the plano-convex lens defined by the top and bottomsurfaces of the local seal 305H. In terms of rays, ray 1408 is incidenton the curved lower surface of local seal 305H, and intermediate ray1409 is bent closer to the normal to this curved surface compared to ray1408. Ray 1409 is subsequently incident on the plane lower surface ofplanarization layer 1407, and emergent ray 1410 is bent away from thenormal to this plane surface, compared to ray 1409. The net effect forthis configuration is a diverging effect as shown.

FIG. 15 shows an embodiment of the present invention in which local seal1505 is impregnated with pigment particles to achieve an optical filterfunction. Panel 1500 may be part of any of a variety of product typesamong those described above, and in particular may be part of a flatpanel display in some preferred embodiments and an illumination sourcein other preferred embodiments. As shown in FIG. 15, 304W is a whitelight emitting element, which may be fabricated as a tandem OLEDstructure. Other elements 301-303 and 308 shown in FIG. 15 aresubstantially similar to those described above in context of FIG. 3. Redlight ray 1501R and green light ray 1501G are absorbed by pigmentparticles, as indicated by the respective X marks on which 1501R and1501G terminate, while blue light ray 1501B emerges without absorption.Thus, a blue filter function is achieved, which may be desirable toobtain a blue pixel in a flat panel display built using a uniform whiteelectroluminescent structure. Of course, red and green pixels maysimilarly be obtained by impregnating the local seal 1505 with suitablepigments or mixtures of pigments.

The filtering function may also be desirable in lighting products. As anexample, a uniform white electroluminescent structure may be built usingblue and yellow-orange emissive layers. Filtering of theelectroluminescent light can be used to adjust the color temperature, orto otherwise tune the emergent emission spectrum for more pleasantappearance. In particular, the same electroluminescent formulation canbe used to produce lighting panels of different color temperature, byvarying the filtering properties of local seals 1505.

Closely related to filtering is the optical color shift function. FIG.16 shows an embodiment of the present invention in which local seal 1605is impregnated with particles of a fluorescent or other color shiftingmaterial, to achieve an optical color shift function. Panel 1600 may bepart of any of a variety of product types among those described above,and in particular may be an illumination source in preferredembodiments. As shown in FIG. 16, 304 is a light emitting element. Theother elements 301-303 and 308 shown in FIG. 16 are substantiallysimilar to those described above in context of FIG. 3. Light ray 1601excites a fluorescent material particle 1602. The re-radiated ray 1603emerges at a longer wavelength. Thus, a color shift function isachieved, which may be desirable to convert blue light to warmer red,orange, or yellow light, decreasing the color temperature of a lightingpanel 1600 to produce a more pleasant hue.

Finally, FIG. 17 shows an embodiment in which local seal 1705incorporates scattering particles 1701 and performs a scatteringfunction. Scattering is recognized as important for increasing lightextraction efficiency for display and lighting products alike. Panel1700 may be part of any of a variety of product types among thosedescribed above, and in particular may be a display panel in somepreferred embodiments and a lighting panel in other preferredembodiments. As shown in FIG. 17, 304 is a light emitting element, whichmay be fabricated as an OLED. The other elements 301-303 and 308 shownin FIG. 17 are substantially similar to those described above in contextof FIG. 3. Scattering particles 1701 which may be provided in the formof a powder of a refractory material mixed with a glass powder paste orsuspension during deposition of local seal material, as shown forexample in FIG. 6B. A wide variety of inorganic and metal materials areavailable and suitable for use as a refractory scattering material, incombination with a low melting temperature glass. Some well-knownmaterials are aluminum oxide, zinc oxide, and silicon. During fusing ofthe glass material, as shown for example in FIG. 6C or FIG. 7A-7C, therefractory material powder particles remain in situ, and can act asscattering particles 1701 in the finished panel 1700. Light ray 1702 isscattered by a scattering particle 1701 and emerges at a different angleas shown by ray 1703. Other light rays, such as 1704, may emerge withoutinteracting with any scattering particles.

Pre-Formed Encapsulation Substrate

FIGS. 25-28 illustrate other approaches to forming lower encapsulationsubstrate 301. In FIG. 25, matrix 308 is prepared with metal oxidecoating 251 on slant surfaces of each opening. Pre-formed glass windows252 are placed in respective openings, as indicated by dashed arrows.Pressure and heat may then be applied to form hermetic glass-to-metallocal seals in each opening. The corresponding steps are illustrated inFIG. 26. At step 261, a blank metal sheet is provided. At step 262, aplurality of holes is formed. At step 263, the slant surfaces of theholes are selectively oxidized. At step 264, glass windows are insertedinto respective holes. At step 265, pressure and heat are applied tofuse the windows to the metal matrix. At step 266, the encapsulationsubstrate is attached to a leak testing apparatus and the quality ofseals is checked.

FIG. 27A-27B show top and sectional views, respectively, of a pre-formedsingle glass-in-metal window element 270. The element 270 comprises aglass window 275 sealed in a metal plate 278. FIG. 27C shows a pluralityof window elements 270 assembled together with joints 271 to form lowerencapsulation substrate 301. Joints may be, for example, weld or solderjoints. In FIG. 28A, the preformed elements 280 are strips havingmultiple glass windows in a metal matrix 288. A plurality of strips maybe joined, by weld or solder joints 281, to form a completeencapsulation substrate 301, as shown in FIG. 28B.

FIG. 29A shows an assembly 290 comprising an array of activeelectro-optical elements 304 formed on flexible lower structure 302,acting as a substrate. FIG. 29B shows lower encapsulation substrate 301,formed separately. FIG. 29C shows assembly 290 joined with lowerencapsulation substrate 301 to form panel 300. The corresponding stepsare shown in FIG. 30. At step 3001, electro-optical array 290 is formedon lower structure 302. At step 3002, lower encapsulation substrate isformed. In some embodiments, step 3002 is performed according to thesteps of FIG. 26. At step 3003, assembly 290 is joined to the lowerencapsulation substrate 301. At step 3004, a top encapsulation structureis assembled onto panel 300. In some embodiments, the top encapsulationstructure may be formed as an integral unit and attached with, forexample, a perimeter seal. In other embodiments, the top encapsulationstructure may be formed in situ above the electro-optical array 290.

Top and Bottom Local Seals

FIG. 31 shows an embodiment of the invention having a lowerencapsulation substrate 301 with local encapsulation seals 305 asdescribed above in context of FIG. 3. Additionally, each electro-opticalelement 304 also has a local seal 315 above it, as described in parentpublication U.S. 2015/0034934 A1. The skilled practitioner willrecognize that various combinations of local seals described in thisdisclosure and the parent publication may also be used.

In some embodiments, each electro-optical element 304 is an emissiveelement, and panel 311 may be a display product or a lighting product.Such embodiments advantageously provide display and/or illumination fromboth sides of panel 311. In some embodiments, having clear local seals315, 305 on both sides of electro-optical elements 304 allows panel 311to be at least partially transparent when the electro-optical elements304 are off. Accordingly, panel 311 may be a transparent display, abacklit display, a transparent lighting panel, or a window havingdisplay, lighting, and/or signage functions in various embodiments.

In other embodiments, electro-optical elements 304 perform light controlfunctions, so that light incident on panel 311 from the top side, iscontrolled by elements 304 and conditioned light is emergent from thebottom side of panel 311. Of course, similar operation is possible withlight incident on the bottom surface of panel 311 and conditioned lightemergent from the top surface. In some embodiments, elements 304 mayincorporate a controllable mirror function, so that conditioned lightemerges from the same surface at which incident light entered panel 311.According to the specific mirror properties of elements 304, light thatis not reflected back through the incident surface may propagate throughelements 304 and emerge from the opposite surface. Other light-controlproperties for elements 304 may include (a) transitions from specular todiffuse reflection, (b) transitions between two or more of: reflective,transparent, translucent, and absorptive states (c) color transitions,(d) polarization transition.

Electro-optical elements may additionally or alternatively incorporatelight sensing functions. For example, a smart window may be controlledso that elements that are in direct sunlight are rendered partially orwholly light-blocking and act as window shades. Elements that are inshadow, such as from neighboring trees or buildings, may be kept at ahigher degree of light transmission, including up to substantially 100%transmission, either translucent or transparent.

Such embodiments enable a wide range of applications, including smartwindows for buildings and vehicles, signage, and heads-up displays.

While specific embodiments have been described in detail in theforegoing detailed description and illustrated in the accompanyingdrawings, it will be appreciated by those skilled in the art thatvarious modifications and alternatives to those details could bedeveloped in light of the overall teachings of the disclosure and thebroad inventive concepts thereof. It is understood, therefore, that thescope of the present invention is not limited to the particular examplesand implementations disclosed herein, but is intended to covermodifications within the spirit and scope thereof as defined by theappended claims and any and all equivalents thereof.

All U.S. patents and patent application publications referenced aboveare hereby incorporated by reference as if set forth in full.

I claim:
 1. A panel product incorporating an active light-emittingregion comprising: a) a substrate comprising: i) a flexible matrixhaving a plurality of openings, wherein each opening has a perimeter;and ii) a plurality of separate rigid local encapsulation seals, whereineach local encapsulation seal fills a respective opening in the flexiblematrix, and is adhered to the perimeter of the respective opening; b) atwo-dimensional array of OLED elements formed over the substrate; and c)a flexible upper encapsulation structure; wherein: first and secondneighboring OLED elements are located directly above separate first andsecond local encapsulation seals respectively, and for any directionfollowing the surface of the substrate, the width of any one of thelocal encapsulation seals along that direction is less than or equal toone tenth the width of the flexible substrate along the same direction.2. The panel product of claim 1 wherein the panel product is atelevision, and the active light-emitting region has extent greater thanor equal to 30 cm.
 3. The panel product of claim 1 wherein the panelproduct is a phone, and the active light-emitting region has extent lessthan or equal to 20 cm.
 4. The panel product of claim 1 wherein thepanel product comprises an information display monitor, and the activelight-emitting region has extent in the range 20 cm to 155 cm inclusive.5. The panel product of claim 1 wherein the panel product is a wearableproduct.
 6. The panel product of claim 1 wherein the panel product is alighting product.
 7. The panel product of claim 1, wherein each localencapsulation seal comprises light-transmissive glass.
 8. The panelproduct of claim 1, wherein exactly one OLED element is located directlyabove each local encapsulation seal.
 9. The panel product of claim 1,wherein the numbers of OLED elements directly above each localencapsulation seal are chosen from the group consisting of three, four,six, and seven.
 10. The panel product of claim 1, further comprising: d)a flexible encapsulation seal formed below the local encapsulationseals, wherein an area of the flexible encapsulation seal encompassesthe active light-emitting region.
 11. The panel product of claim 1,wherein all local encapsulation seals have the same size and shape. 12.A flexible device having an integral two-dimensional array ofelectro-optical elements, the device comprising: a plurality of separatelocal encapsulation seals adhered below respective groups of theelectro-optical elements, wherein: first and second neighboringelectro-optical elements lie directly above separate first and secondlocal encapsulation seals respectively, the aspect ratio of each localencapsulation seal is less than or equal to 2:1, and the maximum numberof electro-optical elements directly above any one local encapsulationseal is not more than 4% of the number of electro-optical elements inthe two-dimensional array of electro-optical elements.
 13. The flexibledevice of claim 12, wherein the electro-optical elements emit light. 14.The flexible device of claim 12, wherein the electro-optical elementscontrol transmission of light, but do not themselves emit light.